The impact of MRI white matter hyperintensities on dementia in Parkinson's disease in relation to the homocysteine level and other vascular risk factors.

BACKGROUND: The role of white matter hyperintensities (WMH) and homocysteine (Hcy) and other vascular risk factors in the pathogenesis of Parkinson's disease (PD) dementia (PDD) remains unclear.

OBJECTIVE: The aim of the study was to assess the impact of WMH, Hcy and other biochemical and vascular risk factors on PDD.

METHODS: A total of 192 patients with PD and 184 age- and sex-matched healthy controls were included. A semistructured interview was used to assess demographic and clinical variables with respect to vascular risk factors (arterial hypertension, diabetes mellitus, atrial fibrillation, ischemic heart disease, obliterative atherosclerosis, hypercholesterolemia, smoking, alcohol intake). Unified Parkinson's Disease Rating Scale score, Hoehn-Yahr staging and the Schwab-England activities of daily living scale were used to assess motor abilities and activities of daily living. A complex neuropsychological examination with a battery of tests was used to classify patients into a group with dementia (PDD) and a group without dementia (PD). Neuroradiological examination of MRI scans included visual rating scales for WMH (according to the Wahlund and Erkinjunntti rating scales) and the Scheltens scale for hippocampal atrophy. Blood samples for Hcy, folate, vitamin B12, fibrinogen, lipids, glucose, creatinine, transaminases and thyroid stimulating hormone (TSH) were examined.

RESULTS: Among all patients, 57 (29.7%) fulfilled the diagnostic criteria for dementia. Significantly higher Hcy plasma levels were noted in PD and PDD groups compared to controls (p < 0.05) and in PDD when compared to PD (p < 0.05). According to multivariate regression analysis, WMH (Erkinjuntti scale), high Hcy, low vitamin B12 and folate plasma levels were independent risk factors for PDD. Vascular risk factors did not play any role in the pathogenesis of PDD and WMH.

CONCLUSIONS: WMH along with Hcy, folate and vitamin B12 may impact cognition in PD. Therapy with vitamin B12, folate and catechol-O-methyltransferase inhibitors may play a potential protective role against PDD.